The invention relates to the field of carding textile fibers on a textile machine and more particularly, to regulating the feed of fibers to a carding machine which produces a sliver or web output having a uniform weight per unit length. Typically, the carded web or sliver has a weight per unit length which is highly uniform. It is desirable to hold weight variations within 5 grams from a prescribed weight. The web weight delivered by the carding machine is usually determined by the relative speed of the card feed roll and the doffer cylinder, and the density of the fibrous mass entering the machine at the feed roll.
Many prior arrangements have been proposed to regulate the feeding of the fibrous mass by the card feed roll. A thorough discussion of these arrangements may be had by reference to U.S. Pat. No. 4,275,483. This patent proposes, among other things, to sense the thickness of the fibrous mass, between the nip of a movable feed roll and a fixed feed plate by sensing the linear displacement of the feed roll. However, this requires that the feed roll be mounted to the frame of the carding machine in such a manner that the bearings are displaceable. The result is a more complicated mechanical structure at the infeed of the carding machine. If displaceable, the feed roll must be weighted satisfactorily against the fibrous mass. U.S. Pat. No. 4,506,413 uses a displaceable feed plate and fixed feed roll arrangement for sensing the amount of fibers fed by the card feed roll. While it is highly desirable to sense and correct the fiber feed at generally the same point, i.e. the feed roll, the arrangements using movable parts have been relatively more complicated and not altogether satisfactory.
It has also been proposed to sense torque on a feed roll by using a strain guage arrangement connected between a drive pulley and a feed roll shaft to sense feed roll torque. The drive pulley is driven by a chain by a remote drive motor. This also results in an arrangement of relative complexity and practicality.
Accordingly, an object of the invention is to provide a simple and reliable sensor for sensing and correcting the quantity of fibers fed to a carding machine at a card feed roll.
Another object of the invention is to provide a sensor for accurately sensing fibers fed by a card feed roll of a carding machine in a highly responsive manner so that the web produced on the machine may be accurately controlled.
Another object of the present invention is to provide a sensor for sensing a reaction force to the forces produced on a card feed roll as an indication of the amount of fibers fed by the card feed roll on a carding machine for use in producing a web or sliver having a uniform weight per unit length.
Still another object of the present invention is to provide a simple and accurate sensor for sensing feed roll torque produced by feeding fibers to a carding machine and generating a control signal that may be used to regulate the speed of the feed roll and to obtain the feeding of a prescribed quantity of fiber.